The disclosure relates generally to Gas Metal Arc Welding (GMAW) and, more specifically, to Metal-cored Arc Welding (MCAW) of mill scaled steel workpieces.
Arc welding is commonly used in numerous applications such as shipbuilding, offshore platform, construction, heavy equipment, pipe mills, and so forth. Certain arc welding processes (e.g., Gas Metal Arc Welding (GMAW) and Metal-cored Arc Welding (MCAW)) utilize welding wire, which generally provides a supply of filler metal for the weld deposit and provides a path for current during the arc welding process. Tubular welding wire, for example, includes a metallic sheath encircling a granular core. In particular, metal-cored welding wires are a type of tubular welding wire that generally produce a substantially slag-free weld deposit, which reduces post-weld processing compared to other types of tubular welding wire, such as flux-cored tubular welding wires.
One type of steel workpiece that is common to structural and heavy equipment applications is hot-rolled steel. Since hot-rolled steel is generally cooled in an oxygen-containing atmosphere, it forms a mixed iron oxide coating layer commonly referred to as mill scale. This mill scale coating provides a barrier layer that, while it remains intact, protects the underlying steel from further oxidation. Before mill scaled steel workpieces are used in a GMAW or MCAW process, they are typically descaled to remove the mill scale coating via pickling or abrasive blasting, which adds significant time and cost to the welding process.